The purpose of this research program is to study the effects of neural and hormonal factors regulating hypothalamic activity. For this purpose the following experiments will be conducted. 1) The effect of localized forebrain lesions on the transmission of somatosensory, photic and acoustic and olfactory impulses which activate adrenocortical responses to be studied in rats. 2) Determination of the role of the septum and the hippocampus in the negative feedback effect of glucocorticoids in the regluation of ACTH secretion, by the production of selective lesions and ablations. 3) Electrophysiological investigation by single cell recording, of the neural connections between the hypothalamus and adjacent limbic structures involved in ACTH regulation, in rats with hypothalamic deafferentations and selective brain lesions. 4) Determination of steroid sensitivity of single cells in the hippocampus, septal nuclei and the hypothalamus in rats and cats as studied by the iontophoretically extracellularly administered cortisol and corticosterone sodium succinate.